Bird Flu Kills Seals

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A research team reports that a new type of avian influenza virus has become capable of infecting harbor seals in New England, a number of whom have died from pneumonia. The group of investigators includes scientists at the Center for Infection & Immunity (CII) at Columbia University’s Mailman School of Public Health, the National Oceanic and Atmospheric Association, New England Aquarium, USGS National Wildlife Health Center, SeaWorld, and EcoHealth Alliance.

The problem was first noticed last September when seals with severe pneumonia and skin lesions suddenly appeared along the coastline from southern Maine to northern Massachusetts. Most were less than six months old and a total of 162 dead or moribund seals were recovered over the next three months.

Pathogen screening with diagnostic tools developed at the CII was conducted in a subset of afflicted seals and a new strain of avian H3N8 influenza virus was identified as a culprit.

Based on full-genome sequencing and phylogenetic analysis, seal H3N8 descended from an avian strain that has been circulating in North American waterfowl since 2002, which implies recent transmission from wild birds to seals. Seal H3N8 has acquired the ability to bind sialic acid receptors that are commonly found in the mammalian respiratory tract. Mutations in the HA and PB2 genes, which are required for cell entry and replication, respectively, suggest enhanced virulence and transmission in mammals. However, the scientists point out that further studies are needed.

Given these findings along with the long history of the spread of avian influenza to humans—most notably H1N1 and H5N1—seal H3N8 could pose a threat to public health, according to the researchers.

“Our findings reinforce the importance of wildlife surveillance in predicting and preventing pandemics”, says W. Ian Lipkin, director of the CII and John Snow professor of epidemiology, at the Mailman School of Public Health. “HIV/AIDS, SARS, West Nile, Nipah, and influenza are all examples of emerging infectious diseases that originated in animals. Any outbreak of disease in domestic animals or wildlife, while an immediate threat to wildlife conservation, must also be considered potentially hazardous to humans.”